US president Donald Trump has said an explosive new book about the first year of his presidency is full of "lies, misrepresentations and sources that don't exist".

Mr Trump was writing on Twitter a day before the release of Fire and Fury: Inside the Trump White House - a book which is said to paint the businessman as a leader who does not understand the weight of the presidency.

Although Mr Trump did not name the book's author Michael Wolff by name, he wrote that he "authorised Zero access to White House (actually turned him down many times)."

"Look at this guy's past and watch what happens to him and Sloppy Steve!," he added, in an apparent reference to former White House strategist Steve Bannon.

Mr Bannon is depicted in the book as questioning Mr Trump's competence and described a June 2016 meeting between Donald Trump Junior, Trump campaign aides and a Russian lawyer as "treasonous".

White House officials described the president as furious at Mr Bannon's criticisms, and White House press secretary Sarah Huckabee Sanders went as far as to suggest that Mr Bannon ought to be ousted from Breitbart, the populist website he helps run.

"I certainly think that it's something they should look at and consider," she said.

Mr Bannon had helped Mr Trump form a coalition of anti-establishment Republicans, blue-collar working class and economic nationalists that launched him to the White House, but Mr Trump had long ago grown frustrated that Mr Bannon seemed to be overstepping his role as a staffer.

Donald Trump with his wife Melania

"Bannon has no contingent," former Republican House Speaker Newt Gingrich said on Wednesday between media interviews to defend Mr Trump after excerpts from the book were published.